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Theoretical study of the tautomerism of 8‐azaadenine
Author(s) -
Contreras J. Guillermo,
Madariaga Sandra T.,
Alderete Joel B.
Publication year - 1998
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/(sici)1099-1395(199806)11:6<392::aid-poc13>3.0.co;2-7
Subject(s) - tautomer , chemistry , polarizable continuum model , computational chemistry , gas phase , solvent effects , solvent , aqueous solution , ab initio , ab initio quantum chemistry methods , thermodynamics , solvation , organic chemistry , molecule , physics
The prototropic tautomerism of 8‐azaadenine (azaade) was studied theoretically by means of ab initio methods, in both the gas phase and aqueous solution. A number of tautomeric forms were not included in the calculations after applying a stepwise elimination procedure based on both AM1 and HF/6–31G* energy values. The tautomers 9 H ‐azaade, 8 H ‐azaade and 7 H ‐azaade survived to this elimination and their optimized geometries and energies were calculated at the MP2/6–31*//HF/6–31G* level. To include the solvent effects, two self‐consistent reaction field method were used: (1) Onsager's SCRF with multipolar expansion up to the hexadecapolar term and (2) the isodensity polarizable continuum method (IPCM). Both methods produce similar results, although the latter represents better the situation in aqueous solution. The stability order in solution, 8 H ‐ > 9 H ‐ > 7H‐azaade, differs slightly from that found in the gas phase, implying that in general the electrostatic effects in solution are important, but the intrinsic stability of these species in the gas phase overcomes the solvent effect. © 1998 John Wiley & Sons, Ltd.